UDP-galactosyltransferase (UDP-galactose:N-acetylglucosamine galactosyl-transferase) is a Golgl membrane-bound enzyme that participates in the coordinate biosynthesis of the carbohydrate moieties of glycoproteins and glycolipids. Galactosyltransferase has also been localized to the plasma membrane of a diverse variety of cells and tissues by immunohistochemical and biochemical procedures. This cell surface distribution has led to the postulate that, in addition to its biosynthetic role, the enzyme also has a functional role in intercellular recognition and adhesion. Analysis of the cell surface galactosyltransferase, localized to the plasma membrane overlying the intact acrosome of mouse sperm, supports a functional role in sperm-egg recognition. Additionally, biochemical data suggest that galactosyltransferase is functionally involved in the mouse T/t locus, a region mapped to chromosome 17, in which mutations lead to abnormal embryonic development and sperm production. This proposal takes advantage of a bovine cDNA clone, recently characterized in our laboratory, which contains about 60% of the coding sequence of galactosyltransferase and hybridizes to both murine mRNA and DNA. The specific aims are to: (1) isolate the complete murine GT gene, (2) determine the mRNA structure, (3) determine its genomic organization, (4) map its chromosomal location and, (5) analyze the expression of murine galactosyltransferase during early normal mouse development by RNA in situ hybridization, in combination with immunohistochemical localization. Our long range objectives are to define the structure, function and organization of this enzyme in both its Golgl and plasma membrane compartments, to determine the mechanism(s) responsible for the compartmentalization of this membrane-bound enzyme and to understand the role of the cell surface GT in mouse development and its relationship to the T/t locus. The proposed experiments lay the foundation for our long range goals.